Chapters 6 and 7: Cellular Energy, Enzymes, and Redox Reactions

Vocabulary flashcards covering energy types, thermodynamics, enzyme kinetics, chemical equilibrium, and redox processes from Chapters 6 and 7.

Catabolic pathways

Metabolic pathways that break down large molecules into small molecules, which are often exergonic and involve ATP and NADH.

Anabolic pathways

Metabolic pathways that build large molecules from small molecules, requiring energy and utilizing ATP to drive the process.

Kinetic energy

The energy of motion, exemplified by a moving car.

Thermal energy

Energy associated with heat, such as body heat.

Potential energy

Stored energy resulting from position or structure, such as $H_2O$ held behind a dam.

Chemical energy

Potential energy stored in chemical bonds, such as in glucose.

First law of thermodynamics

The principle stating that energy cannot be created or destroyed, only transferred or transformed.

Entropy

A measure of disorder or randomness in a system; more organized states possess less entropy, while less organized states possess more entropy.

Second law of thermodynamics

The principle stating that overall entropy in the universe tends to increase over time.

Free energy

The portion of energy in a system available to do work.

Exergonic reaction

A reaction where energy is released ($\Delta G$ is negative, transitioning from high to low free energy), making it spontaneous.

Endergonic reaction

A reaction requiring energy input (transitioning from low to high free energy), making it non-spontaneous.

Spontaneous reaction

A reaction that is thermodynamically favorable and can proceed without an additional energy input.

Non-spontaneous reaction

A reaction that requires an input of energy to proceed forward.

Adenosine triphosphate (ATP)

The cell's primary energy-coupling molecule, composed of adenine (a nitrogenous base), ribose (a 5-carbon sugar), and three phosphate groups.

Energy coupling

The pairing of an exergonic process with an endergonic process to provide the necessary energy for reactions requiring an energy input.

Transition state

A temporary high-energy state that reactants must enter before they can be converted into products.

Activation energy

The energy required for reactants to reach the transition state; reactions requiring more activation energy are slower, while those with less proceed faster.

Enzymes

Catalytic agents that increase reaction rates and help reactions reach equilibrium faster by lowering activation energy without altering $\Delta G$ or being permanently consumed.

Substrate

The specific molecule upon which an enzyme acts.

Active site

The region on an enzyme where the substrate binds due to complementary shape, chemical properties, charges, bonds, and interactions.

Induced fit

The slight conformational change an enzyme undergoes upon substrate entry into the active site to produce a tighter, better fit.

Enzyme inhibitor

A regulator that decreases enzyme activity by either binding to the active site or binding elsewhere to alter the enzyme's shape.

Enzyme activator

A regulator that binds to an enzyme to increase its catalytic activity.

Chemical equilibrium

The state where forward and reverse reaction rates are equal, resulting in constant concentrations of reactants and products with no net change.

Cellular equilibrium prevention

The strategy by which cells continually supply reactants and remove or utilize products to keep reactions moving forward and maintain their ability to perform work.

Cellular respiration

An exergonic process with negative $\Delta G$ represented by $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}$, where high free energy glucose is oxidized and oxygen is reduced.

Oxidation

The loss of electrons during a chemical reaction, exemplified by $NAD^+$ in its oxidized form.

Reduction

The gain of electrons during a chemical reaction, exemplified by NADH which has gained electrons.